What are the indications and precautions for prescribing chlorhexidine (CHX) for oral health, considering its impact on normal bacterial flora of the mouth and gastrointestinal (GI) tract?

Chlorhexidine for Oral Health: Indications and Impact on Bacterial Flora

Chlorhexidine mouthwash (0.12-0.2%) should be prescribed as a short-term adjunct to mechanical oral hygiene when mechanical debridement is not possible, primarily for gingivitis prevention and plaque control, but should not be used long-term due to significant adverse effects including tooth staining and uncertain effects on oral flora. 1

Primary Indications for Chlorhexidine

Post-Surgical and Acute Conditions

• Post-periodontal surgery: 85% of dentists recommend chlorhexidine frequently after surgical periodontal procedures 2
• Acute gingivitis: Used by 74% of practitioners for acute inflammatory episodes 2
• Post-oral surgery: Recommended in 57% of general oral surgical cases 2
• Denture care in hospitalized patients: Soak dentures for 10 minutes in 0.2% chlorhexidine before insertion 3
• Prevention of post-extraction bacteremia: A single pre-procedural rinse reduces bacteremia from 96% to 79% at 30 seconds, and from 20% to 2% at 1 hour 4

Specific Clinical Scenarios

• Stomatitis and herpes simplex infections: Used frequently by 73% and 54% of practitioners respectively 2
• Stevens-Johnson syndrome/toxic epidermal necrolysis: Antiseptic oral rinse containing chlorhexidine twice daily is recommended 3
• When mechanical oral hygiene is compromised: Ideal prophylactic when toothbrushing is not possible 1

Adjunct to Periodontal Therapy

• Non-surgical periodontal treatment: Used by 35% of practitioners as an adjunct 2
• Mild gingivitis (Gingival Index score of 1): Reduces gingivitis by 0.21 on the 0-3 GI scale at 4-6 weeks 5
• Plaque reduction: Produces a large reduction in plaque (SMD 1.45 standard deviations) at 4-6 weeks 5

Critical Limitations and Contraindications

NOT Recommended For:

• Treatment of established oral mucositis: Chlorhexidine is not recommended for treating established mucositis 3, 6
• Prevention of radiation-induced mucositis: Not recommended in head and neck cancer patients undergoing radiotherapy 3
• Prevention of mucositis in HSCT patients: GM-CSF mouthwashes containing chlorhexidine are not suggested 3
• Ventilator-associated pneumonia prevention: No formal recommendation issued due to unclear balance between potential pneumonia reduction and potential mortality increase 3
• Pre-procedural antimicrobial rinses: No recommendation offered for preventing clinical infections among dental healthcare providers or patients, as scientific evidence is inconclusive 3

Impact on Normal Bacterial Flora

Oral Flora Effects

Immediate antimicrobial action: Approximately 30% of chlorhexidine is retained in the oral cavity after rinsing and slowly released into oral fluids 7

Paradoxical rebound phenomenon:

• Chlorhexidine causes a dramatic immediate reduction in epithelial cell-adherent bacteria 8
• However, one day after chlorhexidine rinse, viridans streptococci numbers exceed baseline levels 8
• This delayed, temporary increase in oral viridans streptococci should be considered a possible risk factor in medically compromised patients 8

Long-term flora stability:

• Six months of use did not result in significant bacterial resistance, overgrowth of opportunistic organisms, or adverse changes in the oral microbial ecosystem 7
• Three months after discontinuation, bacterial counts and resistance levels returned to baseline 7
• General reduction of aerobic and anaerobic bacteria ranging from 54-97% during use 7

Gastrointestinal Tract Impact

Minimal systemic absorption: Chlorhexidine is poorly absorbed from the gastrointestinal tract 7

Excretion pattern:

• Approximately 90% excreted through feces 7
• Less than 1% excreted in urine 7
• Peak plasma level of only 0.206 µg/g reached 30 minutes after ingesting 300 mg dose 7
• No detectable plasma levels 12 hours after administration 7

Clinical significance: The poor GI absorption and primarily fecal excretion suggest minimal disruption to intestinal flora, though this has not been extensively studied in the available evidence.

Optimal Prescribing Protocol

Concentration and Frequency

• Concentration: 0.12-0.2% formulations are recommended 1
• Higher concentrations (>0.2%) unnecessarily increase adverse effects without additional benefit 1
• Frequency: Twice daily (morning and evening after toothbrushing) 7, 2
• Duration: 30 seconds of rinsing 7
• Volume: 15 mL undiluted 7

Administration Instructions

• Rinse after toothbrushing, not before 7
• Do not rinse with water, use other mouthwashes, brush teeth, or eat for 30 minutes after use 7
• Expectorate after rinsing; not intended for ingestion 7
• Use alcohol-free formulations to minimize irritation 3

Adverse Effects Profile

Common and Expected

Extrinsic tooth staining (most significant concern):

• Large increase in staining at 4-6 weeks (SMD 1.07 standard deviations higher) 5
• Reported as major concern by 77% of dentists 2
• Affects teeth, restorations, and tongue 2

Other frequent adverse effects:

• Taste disturbance/alteration (reported in 11 studies) 5
• Oral mucosa effects: soreness, irritation, mild desquamation, ulceration/erosions (13 studies) 5
• Burning sensation or burning tongue (9 studies) 5
• Dryness of mouth (6% of practitioners report patient complaints) 2
• Calculus buildup (results inconclusive but reported) 5

Management of Adverse Effects

• For chlorhexidine-induced sore throat: Stop chlorhexidine immediately 6
• Use benzydamine hydrochloride spray every 3 hours for symptomatic relief 6
• Apply white soft paraffin ointment to lips every 2 hours if irritated 6
• Warm saline mouthwashes for cleansing and soothing 6

Duration of Therapy

Short-term use is preferred:

• Initiate directly following dental prophylaxis 7
• Re-evaluate and provide thorough prophylaxis at intervals no longer than 6 months 7
• For long-term periodontitis treatment (stage I-III), chlorhexidine chips are recommended over mouthwash 1

Common Pitfalls to Avoid

1. Do not prescribe for established mucositis: Chlorhexidine is ineffective for treating existing mucosal injury 3, 6
2. Avoid long-term continuous use: Leads to significant staining and other adverse effects without clear additional benefit 5
3. Do not use in ventilated patients without careful consideration: Potential mortality concerns in ICU settings 3
4. Warn patients about the rebound increase in streptococci: Particularly important in immunocompromised or cardiac patients 8
5. Do not use concentrations >0.2%: No additional efficacy but increased adverse effects 1